239.  The principle of working of a transformer is
A. mutual induction
B. static induction
C. self induction
D. dynamic induction

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240.  Which of the following is not a fitting on a transformer?
A. Commutator
B. Breather
C. Conservator
D. Buchholz's relay

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241. In a transformer an insulating material may fail due to
A. moisture
B. dust
C. voids in the winding
D. any of the above

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242.  The reactance of a transformer depends on
A. leakage flux
B. size of the core
C. size of the tank
D. all of the above

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243. Buchholz relay is used in
A. motor protection
B. line protection
C. transformer protection
D. none of the above

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244.  Which of the following parts of a transformer is likely to suffer maximum damage due to excessive temperature rise?
A. Winding insulation
B. Copper winding
C. Core laminations
D. Dielectric strength of oil

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245.  In a transformer on no-load, the input voltage
A. is always at 600 to the magnetizing current
B. is in phase with magnetizing current
C. leads the magnetizing current by 90?
D. lags the magnetizing current by 90?

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